Predicting Growth Can Confound Experts

Like an adolescent child with unpredictable growth spurts, the Orlando area can confound those trying to figure out its size from year to year.

One study describes the Orange-Osceola-Seminole County area as the 14th fastest-growing in the nation. Another says it is now the third.

One group of forecasters says to expect a 50 percent jump in population by the year 2000; another predicts a 67 percent increase by 2005.

All agree on one thing: This kid is growing fast.

The picture is the same throughout the state. Fort Pierce, Fort Myers, Ocala, Sarasota, West Palm Beach, Naples and Daytona Beach all have made it to various spots on recent growth charts.

Florida is unique because most of its growth comes from migration, not natural increases. The trick is determining the future state of the economy in order to predict at what rate people will move here.

The state's diverse economy makes it a natural for continued growth, economists agree. Besides tourism and agriculture, high-tech and defense- related industries and a healthy service economy are expected to fuel migration.

A Commerce Department forecast recently predicted that the metropolitan area of West Palm Beach-Boca Raton-Delray Beach soon will have the fastest growth rate in the nation. A private forecaster, however, said that Greeley, Colo., will hold that position and Fort Pierce in South Florida will be the second-fastest growing area in the country.

In 1984, a Dun & Bradstreet Corp. forecast put Fort Pierce in second place nationally, West Palm Beach in 10th place and Orlando in 19th.

Population forecasts vary because the data always are changing, experts look at different histories, and predictions are made for different time periods and for different numbers of metropolitan areas.

Confusing as the projections can be, they are important. Private companies use them to know how big a market to expect or how much equipment to buy. Governments need them to know how many roads to widen, how many water plants to build, how much housing to plan.

A city without proper population projections may outgrow its new roads and water plants even before they are built.

Still, people who make the projections caution that they should not be held to exact numbers.

''The purpose of projections is to give an idea of what the future will be like, not to precisely pinpoint it,'' said Jane Bucca of the University of Florida's Bureau of Economic and Business Research.

''If we're not completely on the money it doesn't mean the projections were a failure,'' she said.

The university bureau has a contract with the state to estimate state and county populations based on U.S. Census data, electrical customers and building permits and also to make long-range population projections based on standard statistical techniques.

The estimates are vital to local governments. Their percentage of state revenue-sharing dollars is based on them.

Private industry also pays for projections. Companies such as the National Planning Association Data Services of Washington, D.C.; Woods & Poole Economics, also of Washington; and M.G. Lewis Econometrics Inc. of Winter Park, prepare projections for private companies and sometimes make their numbers available to the public.

M.G. Lewis Econometrics president Hank Fishkind said the projection methods are scientific but the conclusions are conditional.

''We build a mathematical model that we have some belief in,'' said Fishkind. But he added, ''I've been doing this for 10 years and I've been wrong plenty of times.''

He compares the process to someone trying to plan how much a family will spend for groceries in the next five years. To do such a forecast, you look at how much you spent in the last five years, how many people are in your family, groceries costs, future prices and your anticipated income.

The idea is to analyze what you have done and what new factors are at work to know where you are going.

Projections are essential for deciding marketing strategies and business expansions. Even if they are not exact, they are big business and many dollars can be made or lost based on them.

Often, a quick glance at a handful of population projections seem to show vastly different conclusions. In fact, much of the information from these studies is similar. The difference is in the way one looks at them.

For example, the U.S. Commerce Department's Bureau of Economic Analysis recently predicted that the Orlando area will be the third-fastest growing area in the nation from now until the year 2000.

Woods & Poole Economics, on the other hand, predicted the area would be the 21st fastest growing in the nation and the third fastest in the state.